Hey, I know a way, actually I am late to this topic a LOT but if anyone wonders how to do the same, here is how you can do it:
first make a value inside player that changes with the fps of player.
then use TopBarPlus, insert it and keep it inside of replicated storage, go to starterplayerscripts and make a script in it, then.
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local Icon = require(ReplicatedStorage.Icon)
local icon = Icon.new()
local plr = game.Players.LocalPlayer
local FPS = plr:WaitForChild("FPS")
icon:setLabel(FPS.Value .. " FPS")
icon:setCornerRadius(0, 8)
icon:setProperty("deselectWhenOtherIconSelected", true)
icon:setLeft() -- type icon:setRight() if you want it at right
icon:lock() -- basically make the label not selectable
FPS:GetPropertyChangedSignal("Value"):Connect(function()
if FPS then
icon:setLabel(FPS.Value .. " FPS")
end
end)
done!